This database study included 171 spontaneous reports from the National Registry of Drug-Induced Ocular Side Effects, World Health Organization (WHO) and FDA on fluoroquinolones and diplopia. The relationship between fluoroquinolones and diplopia was deemed "possible," according to WHO criteria, based on the reported time relationship, multiple positive dechallenge and rechallenge reports and a plausible mechanism of diplopia development: possible extraocular muscle tendinitis. The median time from beginning fluoroquinolone therapy until diplopia onset was 9.6 days.